An operating electric motor produces radial and axial vibrations. Many applications attach the electric motor to a mounting surface that supports and holds the motor in a specific location for a system installation. When the electric motor is so installed, vibrations from the operating motor are transmitted from the motor to the mounting surface by the surface area that is common to the motor and the mounting surface. The mounting surface then transmits these vibrations to other connecting surfaces and fasteners in the system installation. Vibrations from the operating motor that are transmitted to the mounting surface tend to loosen nuts, bolts, screws and other fasteners or connectors that are used in connecting and assembling the system installation. This loosening of fasteners and connectors can adversely effect the system installation.
Motor induced vibrations cause other undesirable effects as well. For example, vibrations from the operating motor and those transmitted by the motor mounting surface can produce an audible noise. In the case of a fan motor mounted to a ducted ventilating system, the generated noise is often transmitted through the ventilating ducts. At a minimum, this noise is distracting and annoying to individuals near the ducting system.
Conventional methods for reducing the transmission of vibrations from an operating electric motor attempt to isolate the motor from the mounting surface by using various vibration isolation systems. One such system uses several mounting screws with washers to attach a motor with an integral motor flange to the mounting surface. The mounting surface has several bosses configured to accept a vibration isolating grommet having a grommet insert or bushing inside. The motor flange is configured to fit around the mounting surface bosses. The mounting screws pass through the grommet inserts, and attach to the mounting surface while the mounting screw washers contact and hold the isolating grommets and the motor flange to the mounting surface. Unfortunately, this vibration isolation system has a significant amount of surface area common to the motor flange and the mounting. The common surface area acts as a medium through which motor vibrations are transmitted to the mounting surface. Moreover, aligning and installing such an isolating system can be cumbersome and time consuming when more than two mounting screws are required for installation.
Another conventional vibration isolation system locates the motor inside a rigid housing having a flanged opening and a closed end with at least two retaining holes. The motor has at least two retaining holes in a surface opposite its drive shaft surface. The motor is positioned inside the housing such that the drive shaft of the motor extends through the flanged opening of the housing and at least two retaining screws pass through the housing retaining holes and attach to the motor retaining holes. Typically, vibration isolation material is located between the rigid housing and the mounting surface. The housing is attached to the mounting surface using any of a variety of fastening means such as conventional mounting screws, nuts and bolts and the like. Unfortunately, this vibration isolation system also has a significant amount of surface area common to the rigid housing and the mounting surface. Even though vibration isolating material is located between these two surfaces, this common surface area still acts as a medium to transmit motor vibrations to the mounting surface.
Typically, these conventional vibration isolation systems do not significantly reduce motor induced vibrations and tend to increase the total cost, weight and overall package size of the installed system. For most system installations, even a modest increase is undesirable.
Accordingly a need exists for a low cost, lightweight, vibration isolation system that significantly reduces the transmission of vibrations from an operating electric motor without significantly increasing the overall package size of the installed system and is desirably easy to install.